The potential applications and recognized advantages of employing electrical energy in surgical procedures continue to increase. In particular, for example, electrosurgical techniques are now being widely employed to provide significant localized surgical advantages in open, laparoscopic, and arthroscopic applications, relative to surgical approaches that use mechanical cutting such as scalpels.
Electrosurgical techniques typically entail the use of a hand-held instrument that contains one or more electrically conductive elements that transfer alternating current electrical power operating at radio frequency (RF) to tissue at the surgical site, a source of RF electrical power, and an electrical return path device, commonly in the form of a return electrode pad attached to the patient away from the surgical site (i.e., a monopolar system configuration) or a return electrode positionable in bodily contact at or immediately adjacent to the surgical site (i.e., a bipolar system configuration). The time-varying voltage produced by the RF electrical power source yields a predetermined electrosurgical effect, such as tissue cutting or coagulation.
During electrosurgical procedures electric current flows through one or more conductive elements, the active electrodes, and transfers electrical current to tissues, often with coincident sparks or arcs of electricity occurring between one or more electrodes and tissues. The overall process causes heating of tissue and the electrode metal. Tissue heating causes tissues to break into fragments or otherwise change into materials that generally differ physically and chemically from the tissue before it was affected by electrosurgery. The tissue changes at the surgical site, such as charring, interfere with normal metabolic processes and, for example, kill tissues that remain at the surface of incisions. The changes in tissues caused by electrosurgical energy, such as killing parts of tissues, are known to interfere with healing at the surgical site.
Beyond damaging tissue at the surgical site, conventional electrosurgery has other drawbacks which limit its applicability or increase the costs and duration of procedures. Induced heating of tissues and electrodes causes smoke plumes to issue from the tissue. Smoke obscures the field of view and hinders surgical procedures and is also a known health hazard. Controlling smoke once it has formed is problematic, requiring the evacuation of large volumes of air in order to capture an appreciable fraction of the smoke with wands that are close to the surgical site where they are in the way, and adds costs in both additional equipment and labor.
The induced heating also generally causes tissue that has been altered by electrosurgery to adhere to and partially coat electrosurgical electrodes. The tissue fragments that adhere to electrodes and coat the electrodes is called “eschar.” The coatings on blades that form from tissue and tissue fragments are typically rich in carbon and contain various compounds that tend to make the coatings electrically conductive when energized by the type of power used for electrosurgical procedures. Eschar inhibits the effectiveness of electrosurgical devices and must frequently be removed, hindering surgical procedures.
Despite advances in the field, electrosurgical blades continue to suffer from one or more of the problems of producing smoke, having materials from tissues coat the blades, and damaging tissue. Therefore, a need exists to improve performance in each of these areas. Historically, electrosurgical blades have generally not given consideration to the chemical reaction environment and conditions that occur where the electrosurgical energy interacts with tissue by considering factors such as the propensity of tissue to become trapped in regions that lead to prolonged residence times at reactive conditions that lead to producing smoke and materials that coat blades to form eschar. Likewise, prior art electrosurgical blades did not consider the conductive pathways that can be formed by tissue fragments adhering to blades and the effects that these built-up conductive pathways have on producing smoke, producing more materials that can further coat blades, and the effects that these have during electrosurgery.
The aforementioned limitations in conventional electrosurgery impose limits on the peak voltage that can be applied to tissue during electrosurgery.